NVIDIA Adaptive VSync Technology Review

NVIDIA has developed a new technology called Adaptive VSync that is poised to improve the gameplay experience. We look at how this technology works, and see if we can graph the performance and compare it with traditional VSync methods. Check out how this technology is moving the "smoother" gameplay experience forward!

Introduction

With the release of a next generation GPU or video card we expect that the new video card will deliver faster framerates, better acceleration of shader programs, and other techniques to enhance performance. As gamers we want next generation video cards to provide better performance so that game developers can incorporate better graphics and shader programs to make games look better. The new GeForce GTX 680, the first GPU based on NVIDIA's Kepler architecture, has done exactly this.

We've looked at the GeForce GTX 680 in terms of performance and overclocking. The GeForce GTX 680 has proven to be a competitive video card at its $499 price point, delivering better performance than the previous GeForce GTX 580 did when it was launched at the same price point. NVIDIA did not stop with just relying on performance improvements to carry the GeForce GTX 680 and Kepler architecture forward. NVIDIA has three key bullet points in which the GeForce GTX 680 improves not only performance, but also the gameplay experience. To us, and to gamers everywhere, improving the gameplay experience delivered is just as important as improving raw performance.

The first bullet point that NVIDIA makes clear is that the GeForce GTX 680 is "Faster" than previous generations. Under that category NVIDIA includes its SMX architecture and GPU Boost as the key technologies in making the GeForce GTX 680 faster. The second bullet point meant to express improvements in the gameplay experience is the "Smoother" aspect of the GeForce GTX 680. Under that category the key technologies listed are FXAA technology and Adaptive VSync. We've written about FXAA in the past and discussed its benefits to the gameplay experience. This article is going to focus on the Adaptive VSync technology. Finally, the third bullet point is "Richer." Under this category NVIDIA lists Single GPU 3D Vision Surround and PhysX as the key technologies to provide a richer experience.

This article today is going to focus on the "Smoother" aspect of NVIDIA's goal to improve the gameplay experience with the GeForce GTX 680. We will be looking at Adaptive VSync in the best way we can, to test it and to see if it really does improve the gameplay experience.

Adaptive VSync

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The first thing we need to do is tell you is what Adaptive VSync is, and how it works. The goal of this technology is simply to make gaming framerates smoother and improve playability without showing onscreen "tearing." Importantly you will want to know that Adaptive VSync is not tethered solely to the GeForce GTX 680. In fact, Adaptive VSync is part of the Release 300 drivers and is compatible with GTX 680 and prior generation GeForce GPUs. Since it was introduced with the GTX 680 we will use a GTX 680 to test the technology.

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In order to understand what this technology does we must first understand what VSync is and the two options we had previously in games. Without getting into detail that will bore our readers, VSync deals with the native refresh rate of your display and how the game renders its frames. There have been, up to now, only two options for VSync in games. Either you played with VSync on or you played with VSync off. Both on or off has its pros and cons for gaming. With VSync off, your games performance (i.e. framerate) is able to exceed the native refresh rate of your display. The common refresh rate on displays is 60Hz, hence 60 FPS. There are new displays today, especially those of the 3D nature, which run at 120Hz, or 120 FPS. While these new displays are becoming more popular, we are going to focus on the more common 60Hz example.

VSync turned off sounds like a good thing, because your framerate is able to go as high as physically possible from your video card. However, there is a major drawback to allowing framerate to exceed the refresh rate of your display. The consequence is called "tearing," and it is a very real visual anomaly that you will notice more as you play your games as the framerate exceeds the refresh rate. Tearing is described as a frame literally breaking in half, or sometimes even in three parts, and part of the frame lagging behind the other part of the same frame. The result is a visually distorted image that can bother gamers. Note that tearing can technically occur if the framerate doesn't exceed the refresh rate, but it is much less likely to be noticed.

The cure to tearing is to turn VSync on. What this does is cap the game's framerates to the highest native refresh rate of your display. This means on our 60Hz display, the game won't exceed 60FPS. As most people consider 60 FPS to be a very smooth gameplay experience, this sounds like there would be no drawbacks, but unfortunately there is. The problem with turning VSync on is that the framerate is locked to multiples of 60. If the framerate drops even just a little below 60 FPS VSync will drop all the way from 60 FPS to 30 FPS. This is a huge drop in framerate, and that large change in framerate becomes noticeable to the gamer. The result is called stuttering, and when you are playing a game that consistently changes between only 30 and 60 FPS, the game speeds up and slows down and you feel this difference and it distracts from the gameplay experience. What's worse is that if the framerate drops ever so slightly below 30 FPS the next step down for VSync is 20 FPS, and then the next step down is 15 FPS.

These are large steps, with no middle-ground for framerate. With VSync turned on, while curing tearing, introduces its own problems. Therefore, up until recently there hasn't been a very good solution. Either you dealt with tearing, or you dealt with sudden FPS drops. There are some add-on logic solutions as well but these have never caught on well. NVIDIA wants to change this VSync issue, and we are glad this is finally being focused on.

Adaptive VSync is a smart VSync on option that has two goals, eliminate tearing, and eliminate the sudden stuttering and FPS drop. It eliminates the cons of VSync off and on, and allows the pros from both methods.

Adaptive VSync in essence dynamically changes between VSync on and off automatically to deliver no tearing above the refresh rate, yet no FPS drop. Quite simply, with Adaptive VSync VSync is turned on, capping the game to the refresh rate of your display. It will cap to 60 FPS on 60Hz displays, or 120 FPS on 120Hz displays. This eliminates tearing. Secondly, if the framerate drops below your refresh rate VSync shuts off and allows your framerate to run in real-time. Then, when the FPS gets back up to your refresh rate, VSync kicks on and keeps the image from tearing.

What this means is that you will always get the best performance out of your games under your refresh rate. You won't be dropping to 30 FPS if the framerate drops slightly under 60 FPS, as VSync natively operates. Instead, if your framerate only drops to 55 FPS, then you will get 55 FPS. Then, when the framerate reaches the refresh rate, VSync kicks on keeping the game from tearing. It is so simple in description that we wonder why it has never been done until now! NVIDIA is the first to provide this technology to deliver a smooth gaming experience with VSync on.

As you might imagine, Adaptive VSync also has the side effect that if the video card isn't rendering over 60 FPS, it will save power. The video card won't have to work as hard as it would with VSync off, and therefore is a power saver in its own right.

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The full whitepaper on the technology is linked above for your reading pleasure.

Control Panel Option

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The option to turn on Adaptive VSync is located in the NVIDIA control panel. We have version 301.24 of the driver installed on our system. You will find five options in the drop down box. The first option is "Use the 3D application setting." This means is that the in-game VSync option (if one) takes precedent. The off option forces VSync off in all games and the VSync on option forces it on in all games, no matter the in-game setting. The "Adaptive" option is the one you want to use to enable Adaptive VSync. It doesn't matter whether VSync is off or on in your game, this setting overrides in-game control settings. The fifth option Adaptive (half refresh rate) will probably rarely be used. This will basically lock your refresh rate at 30 Hz, or 30 FPS, and most gamers don't want. Using the "Adaptive" option is our preferred option.

Example of Screen Tearing

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In order to understand what we mean by screen tearing, we've created an example from a screenshot in Skyrim that depicts what you'd typically find from screen tearing. In the first image above, the top part of the image is shifted to the left, while the bottom part is shifted to the right. The actual frame has parts of it that lag behind the other parts. These "tear lines" are what you see when fast motion occurs, and the framerate exceeds the refresh rate of your display. It is as if the frame can't keep up with the draw speed of the display, and ends up becoming distorted, where objects and textures no longer line up. Since this occurs in motion, the effect is quite detrimental to the gameplay experience. The second screenshot shows what the image looks like normally. Screen tearing can cause multiple parts of the frame to display out of alignment, such is shown.